Consequences?

dude, it's a movie

As mayaTitan says, it is only a movie... And that's a pity in this case. It is pretty good but too much crap like Arkham Asylum as the old hospital and a Terminator style rampage... It's all too overdone to be really worthwhile.

If we want to ignore the silly excesses, and other ridiculous touches, we have to assume that this story is set in something like the real world. So, if we can do that... Then, the government lacks any X-Files/Area51(alien containment)/MenInBlack or any other silly horseshit. But, after this incident, something of the sort would be set up. No, Madison would not live happily ever after. Being charged with murder would be far better than what might really happen.

That was my thought exactly. It ended abruptly, without answering that question.

It's my feeling that she would be put away in a mental institution for a very, very long time. It's been proven that she had a medical condition, and that she was not totally responsible for the murders. However, they were committed through her so she'll probably face punishment, albeit not in a prison. Not to mention the chance of it happening again is always there so the authorities could not ever permit her to just be free.